In numerous applications, continuous strands or fibers are removed from packages or reels formed on cylindrical supports. The strands or fibers are removed by unwinding them from the outside or inside of the package.
It is very important that the fibers or strands be removed as uniformly as possible. An erratic movement of the fibers can damage them or cause adjacent turns to become tangled. Fiber tangles can result in loops or other discontinuities in the packages and cause processing defects. The removal operation is very delicate because several separate fibers or strands are simultaneously wound on the same support.
The uniform removal of strands or fibers is primarily governed by the manner in which the package of fibers was made. A fiber package is formed by winding at least one strand on a rotating support and simultaneously moving that strand back-and-forth, parallel to the axis of rotation of the support. The proper movement of the fiber is maintained by various guide elements which give the resulting package with its shape.
Some packages have a relatively thick central part tapering down toward the ends of the package to zones of uniformly decreasing thickness. It is not possible to remove separate fibers wound simultaneously on such a package in a uniform manner. When the fiber turns laid down in zones with different diameters unwind, the differences in their lengths cause the formation of loops and, therefore, tangles.
Other packages made using a moving fiber guide have the approximate shape of a cylinder with more or less uniform edges. In such prior art devices, when the guide carrying the fiber or strand back-and-forth reached the end of its travel, there was a very brief period of hesitation before the guide started to move in the opposite direction.
During this period, the turns were superposed on one another and could fall on both sides of a plane perpendicular to the axis of rotation of the support at the end of the travel of the fiber guide. When several separate fibers are wound simultaneously, they can adhere to one another during this brief period of hesitation. During unwinding, such an adhesion modifies the appearance of the fiber, impairing the quality of the products made from it.
On the other hand, if some turns are laid down outside the plane of travel of the guide, they can easily fall out of the edge of the package and be damaged during its storage and handling. During unwinding, such damaged fibers can cause the formation of loops or cause the fiber to break as it is removed.
In applications using packages consisting of several separate glass fibers, as, for example, in the production of cut fibers intended to reinforce materials having a base of polymers or elastomers, or in the production of mat from cut fibers, the quality of the final product is governed in large part by the rate of fiber separation, that is, the ratio between the number of simple fibers obtained on removal and the number of simple fibers initially wound.
The separation rate can vary as a result of partial adhesion of the fibers to one another during the winding process. Fiber adhesion becomes more pronounced in large packages and has led to limitations in package size and weight.
These deficiencies have prompted various proposed remedies to the limitations in prior art manufacturing techniques for cylindrical fiber packages and/or to imperfect fiber separation during winding.
One proposed solution, disclosed in U.S. Pat. No. 4,488,686 to Walter J. Reese, involves modification of the shape of the fiber guide and use of stops positioned at the end of travel of the fiber guide.
According to this invention, the transversing fiber guide is cutout in the shape of a triangle or rhombus. The cutout may even be semicircular or semielliptical in shape. The fiber guide has a central opening through which the fibers or strands are introduced at the beginning of the winding operation.
The fiber drawing installation includes a spinneret filled with molten glass. A large number of glass strands are mechanically drawn from orifices in the spinneret into the shape of elementary filaments. These filaments are joined together into at least two separate bundles which are passed over an oiling device. The bundles are then passed through a gathering device, each bundle becoming a separate fiber. The various fibers thus made are passed into a device provided with notches or any other means to maintain the separation of the fibers during their travel.
The separate fibers are introduced into the head of the fiber guide. During the winding operation, the fibers alternately slide from one side to the other of the cutout in the head of the fiber guide.
Two cylindrical rod stops are positioned on the drive device for the fiber guide, crosswise to the back-and-forth movement of the guide and close to each end of its travel. These stops function to gather the fibers into a single fiber at the end of the package. These gathered fibers forms a sharp lateral package edge practically at right angles to the cylindrical package itself.
A second solution to the problems of package manufacture is proposed in U.S. Pat. No. 4,509,702 to Walter J. Reese. The fiber drawing unit is almost identical to that disclosed in the preceding patent. However, the head of the fiber guide has several slots extending from the periphery of the guide and terminating at an interior curved end which can retain a strand or fiber. The curved ends of the slots are aligned one behind the other in a linear configuration approximately perpendicular to the axis of the support of the package. Each fiber is introduced in a different slot and positively guided during the winding operation.
The stops are placed on the driving device which move the fiber guide when it reaches each end of its travel. This movement of the guide serves to increase the tension on the fibers. Thus, when the fiber guide is in contact with the stops, the fibers are wound on the same turn at the package end. This provides sharp lateral package edges practically at right angles.
In these two patents, there is no disclosure of automatically transferring the fiber winding process from one support to another empty rotating support when the package has reached the desired diameter.